Where to Start: Chassis Powertrain & Transmission

by Tara Baukus Mello //

February 21, 2007

Whatever your reason for building a street rod, it’s a wise move to take some time and create a plan and a budget rather before you start buying parts. Without a plan, you’re likely to buy parts you won’t use later due to mid-stream design changes.

There’s a lot to consider when building a rod – the body, chassis, powertrain, paint scheme, upholstery... Within each area is a multitude of decisions to make. Taking the time to make decisions now will save time and money in the long run.

Speaking of money, developing a budget for your rod is a good place to start. Determine the amount you have available to devote to your project. In the process, consult with your spouse, banker or anyone else involved in your financial decisions. Remember: It often costs more to build a rod than to buy a similar one that is already completed, so it can be misleading to use sale prices as your guide. Once you have your overall budget amount, start browsing through catalogs, street rod company websites, advertisements and swap meets to get see if your estimate is realistic. Don’t forget that this is an estimate for parts – it doesn’t include labor costs, whether it’s your own or a professional you hire. You’ll want to add in any labor estimates you get if you farm out a portion of the work.

Original or Reproduction Body and Chassis
Once you’ve decided on the make and model you prefer, the next step is to decide whether you want to use an original body or a reproduction model. Depending on the make and model you’ve chosen, you may not have a choice. If you want a more unusual vehicle, there may be no reproduction version available. If you’ve selected one of the more popular models, you’re likely to have a choice between original steel as well as both metal and fiberglass reproduction models.

Original bodies are getting harder to come by. When you do find them, they can be quite pricey if in good condition. In my own personal experience, my dad and I began with a ’32 Ford pickup cab that was found in a farmer’s field. Then we used the doors from two other cabs to make a complete cab. Even though we chose the best parts of the group, the doors were in such sad shape that we needed to re-skin the lower portions with new metal. The price was right, but the amount of hours of bodywork we put in on that tiny cab was immense. It wouldn’t have been cost-effective if we had been paying someone for the bodywork.

While reproduction bodies used to be known for their poor quality, these days most are as good as the original, and in many cases much better in fit and finish than originals. Depending on the model, they can be available in steel, fiberglass or both. If you have the luxury of choosing between the two, it’s really a matter of personal preference, though even with new steel, you’ll always have the potential for rust. While it can be done, mixing fiberglass components with steel (such as a steel body and fiberglass fenders), is not recommended because you’re likely to experience challenges when fitting the components together.

If you decide to use a reproduction body, ask fellow rodders about their experience with the company. Ask about the fit, how much body work they had to do and if the manufacturer followed up with the owner during the build process. Then talk to the manufacturers themselves, advises Barb Davison, owner of Outlaw Performance. She suggests that you “ask what the differences are between their bodies and their competitors. If they cost more, ask why they are worth it. Visit the manufacturer at their facility or at a car show, so they can visually show you the differences.” Most companies will give references upon request.

Regardless of what company you choose to do business with, be sure to ask if the reproduction body is built to the original specifications. If the answer is yes, you’ll always be able to source replacement parts, even if that company goes out of business.

When selecting a chassis, you’ll face many of the same issues and questions as when you chose the body. Many people believe that original frames could not possibly be strong enough to be safe, but it really depends on the rod. According to Jim Donovan, co-owner of Chassis Engineering, most frames are secure with up to a 500 hp engine if they’re in good condition. Two notable exceptions to the rule are Model A Fords and ’32 Fords.

Just because a stock Model A or ’32 Ford chassis won’t handle massive amounts of modern horsepower doesn’t mean you have to trash the original frame and buy a stronger reproduction unit. Manufacturers such as Chassis Engineering sell kits to strengthen these frames and bring them up to acceptable standards for handling a powerful V-8. If you’ve located an original steel body – and it still retains its original frame – consider using the chassis for your project as well. According to Donovan, keeping the body and chassis together will give you the best fit possible.

Another commonly held myth is that you have to weld engine or transmission mounts to the original frame being used and that you can’t just bolt on the required mounts or bracing. In reality, nothing should be welded to a ’36-’54 Chevrolet frame because those frames used a thin metal that becomes brittle when heated. Instead, these frames should be modified or upgraded with aftermarket bolt-on components. With Ford frames, you have the flexibility of either welding or bolting the necessary parts, but it’s safe to use the bolt-on option for rodders who would prefer not to put their welding skills to the test.

Assessing the condition of an original frame can be a challenge. Donovan recommends doing a visual inspection, paying close attention to any areas where mud can collect and noting any holes or areas that are thin from rust. Then make the frame as level as possible and measure from the ground up in multiple locations to see if it is twisted. Variances of up to ½-inch are not unusual and can be corrected.

If you’re buying a reproduction body, you’ll most likely need a reproduction frame as well. One way to ease the process is to work with a company that can provide a kit with both the chassis and body. That way you’ll know that the body has been tested and trial-fitted for that chassis. “All you need is something minor off on one jig and it won’t fit right,” explains Davison. Some kits also include different suspension setups and, in many cases, these will also have been tested to reduce fit issues. If you do buy the frame, body or suspension separately, you may want to consider having the manufacturer mate the body to the chassis. A number of companies, including Outlaw Performance, offer this service, which can save the first-time rodder major headaches.

Creating a Rolling ChassisSteering is a critical component in getting your chassis mobile. Some rodders opt to save a few dollars by purchasing a used steering system from a junkyard or swap meet. Whether you’re talking a steering box or rack-and-pinion design, purchasing a used system can be tricky if you don’t know its history. Be sure to check the mileage on the donor vehicle and inspect the steering system carefully for signs of wear. Because this is one of the most critical components in the safety and drivability of your rod, consider buying a new steering system if you can afford it.

Regardless of whether the system you choose is new or used, you still have to make it work in your vehicle. The most common type of system rodders use is a rack-and-pinion, so we asked Ron Domin, vice president of Flaming River Industries, about the challenges rodders most frequently face when installing these systems. He said that he sometimes sees rack-and-pinion front-steer racks installed as rear-steer and vice versa. Be sure you know if the rack you’ve purchased is intended to be installed in front or in back of the front crossmember. If it’s installed incorrectly, the driver will have to turn the steering wheel the opposite direction from where he wants the vehicle to turn, creating a potentially dangerous situation.

Domin also noted that the OEM Mustang II power racks are often very sensitive at higher speeds in rods, which can also be hazardous during an emergency driving maneuver. Manual racks, on the other hand, can make parking or other low-speed maneuvers a challenge. Aftermarket Mustang II racks usually don’t have this sensitivity. Another option is to use an electric version, which the driver can adjust to suit his needs during various driving situations, even within the same trip. At press time, Flaming River was the only company manufacturing an electric rack-and-pinion system for aftermarket use. Electric systems are always handy if you don’t have room for all the hoses, pumps and pulleys required for the power rack, but want more maneuverability than a manual system.

One of the key features all rodders need to determine is the arrangement of the steering column, shaft and universal joints. With the driver’s seat you’re planning on using temporarily installed, Domin recommends creating a mockup using 3/4-inch dowel, duct tape and cardboard to determine the correct positioning. Cut the cardboard in a circle – the exact diameter for the steering wheel you’ll be using – and then tape it to a length of dowel that travels about 3-½ inches through the firewall. The mockup will allow you to determine the length of the column and column drop you’ll need to allow the primary driver a comfortable and safe driving position.

Use the remaining dowel to determine the angles for the universal joints in the steering shaft and the connection to the rack. Ideally you’ll want to use two joints, but three is acceptable. If you have to use angles, Domin notes that 15 degrees is ideal. In addition to having the primary driver on hand for fitting, in order for your mock-up to be accurate, you’ll need to know where your engine’s exhaust headers will be, so you can be sure that the steering shaft doesn’t interfere with them.

There are a wide range of suspension choices that will fit under the most popular street rods. Some rodders opt for sticking with the same brand as the body, while others prefer to mix-and-match based on what they have easy access to and is cost effective. By far the most common suspension choice is a Ford Mustang independent coil-over front suspension and a Ford 9-inch rear end, though the Ford 8-inch can often be used as well. Some rodders opt for a traditional dropped solid front axle, which is less expensive and gives a cleaner look if you are building a highboy.

Even with the front and rear suspension selected, you’ll still need to make a lot of decisions about other suspension components. Springs, crossmembers, shocks, sway bars and some method of locating the rear suspension, such as four-link systems and ladder bars, are just a few of the items to think about. Body and chassis kits can ease the process of choosing all these components, as the kits can be purchased with all the major suspension components necessary. Many of them come installed, also making the building process easier.

No matter what engine package you decide to use, you’ll want to make sure that you have plenty of power to bring your rod to a stop. A combination of front disc and rear drum brakes, or four-wheel disc brakes, are the two setups most frequently used by rodders. They’re inexpensive, easy to service and provide solid stopping power. Although you can use a factory new or reconditioned OEM setup, there are many aftermarket kits available as well. In addition to ensuring all the components use modern technology, these kits also have different looks, like aluminum components for a hi-tech rod or with a vintage-look exterior with new components hidden inside for a nostalgic rod.

The final step in building a rolling chassis is the wheels and tires, which play a huge part in conveying your rod’s “first impression.” There are so many wheel manufacturers that you’ll be faced with a mind-boggling range of choices. Surf the manufacturers’ websites or print catalogs and narrow down your favorites. Be sure that your choices coordinate with the theme you intend on using.

To allow for production and shipping time, order your wheels at least two months in advance of when you expect to need them. Keith Kern, director of sales and marketing at Billet Specialties, suggests calling the manufacturer directly to ask about lead times – even if they don’t sell directly to the end-user – to make sure the answer you get is accurate.

When ordering your wheels, remember that the wheel width refers to where the bead seats on the tire. For example, a 17x8 wheel is actually 9 inches wide from edge to edge. Kern cautions against assuming that an off-the-shelf wheel will fit. “Sizing is not universal through all brands. There could be a 1/4- or a ½-inch difference,” he says. It’s best to get a sizing guide from the manufacturer and measure according to their directions to be sure the sizing is right for your rod.

Your rod’s overall style, as well as the chosen wheel design, will play a large role in tire selection. For example, if you’re going with a modern style and running large diameter wheels, consider opting for a low-profile tire to complete that look. If you’re building a nostalgic rod, maybe choose a set of whitewall or bias-ply tires with a much taller profile.

Just because you’re building a nostalgic rod doesn’t mean you should run old tires purchased at a swap meet or a garage sale. A better solution is to buy vintage-look tires that are made with modern compounds. The largest supplier of this type of tire is Coker Tire, which has the molds for many old tires, and also creates new designs with a vintage look. A newly manufactured bias-ply tire from Coker, for example, will provide you greater mileage than the original, will wander less and is safer than the old bias-ply tires.

Regardless of what tires you choose, you need to consider the load carrying capacity, especially if you opt to run a smaller diameter wheel in front than in the back to get the “rake” that is so popular on street rods. “When you run ‘big ’n littles,’ you end up with lots of unsprung weight on the front end, and you need to make sure that your tires can carry the load of the engine,” explains Corky Coker of Coker Tire.

Building the PowertrainYour rod will need a reliable powerplant that will perform equally as well on the open road as in the slow-moving traffic that’s so much a part of daily driving, some cruises and even many rod shows. You can opt for just about any engine and transmission combination you like, so long as you can make it fit. If you have experience with a specific engine then, by all means, choose that powerplant. After all, you’re going to be the one responsible for maintaining it and diagnosing any problems.

The small-block Chevy V-8 – especially the 350 cubic inch version – is by far the most popular engine for a street rod. For the first-time rodder, using this engine for your rod will mean far fewer headaches. It’s easy to work on, affordable and fits well in most street rods.

There are numerous aftermarket companies offering an immense array of parts for small-block Chevy engines, making it easier to do your own work or to find replacement parts should you break down in some remote location. You’ll also have a much wider selection of mechanics to choose from if you opt to rebuild an older small-block Chevy or decide to undergo some high-performance modifications.

Choosing a Transmission
Like engines, when it comes to transmissions, there are a multitude of options. Although most rod-builders opt for automatic transmissions, there are also a variety of manual transmissions available. However, if you opt for the small-block Chevy engine, you’ll find that the Turbo 350 automatic is the popular choice because its size and shape makes it a nice fit under most rods and reduces the need for a transmission “hump” in the floor. If you go this route, look for a later-model unit, which came with a lockup converter. The Turbo 350 is inexpensive and easy to work on, so even beginners can change the shift points or raise the torque converter stall speeds thanks to a wide array of aftermarket products.

If you prefer to be a bit more modern and want a transmission with automatic overdrive, the top choices for the Chevy 350 engine are the 700-R4 or the newer 4L60. Both of these transmissions have four forward gears, giving them the benefit of good acceleration combined with the top gear for improved fuel economy over the Turbo 350. These units can also be upgraded with aftermarket parts.

The equivalent transmissions for Ford engines are the C-4 and C-6 or the Automatic Overdrive units, known as AOD. For those using other engines, in many cases it makes sense to stick with transmissions from those manufacturers. However, adapters are available to make virtually any engine and transmission combination possible. Once the engine and transmission are selected and trial fitted, you’ll want to measure for a drive shaft. A local drive-shaft shop can either modify a used component or make a new one for you.

Next month, we will address “Completing the Look,” which tells about the two remaining areas to address to finish your concept: paint and interior.